1. Technical Field
The present invention relates to a semiconductor device and a method for manufacturing the semiconductor device.
2. Related Art
In a semiconductor device that has a multilayer interconnect structure including copper interconnects and low dielectric interconnect layer insulating films, films of the same material are normally used for the interconnect layer insulating films and an interlayer insulating film. An example of such a semiconductor device is disclosed in “Proceedings of the 2008 IITC (International Interconnect Technology Conference), Jun. 2-4, 2008, 2.5, p.p. 15-17”.
According to Japanese Laid-Open Patent Publication No. 2007-214403, a diffusion preventing film with compressive stress is formed to cover embedded interconnects after the formation of those interconnects, and a heat treatment involving ultraviolet irradiation is then performed. In this manner, the hardness and elastic modulus of the interconnect layer insulating films are increased.
According to Japanese Laid-Open Patent Publication No. 2006-319116, after embedded interconnects are formed, ultraviolet irradiation is performed on the interconnect layer insulating films to lower the density in the upper portions of the interconnect layer insulating films and reduce the capacitance between the interconnects. By the technique disclosed in Japanese Laid-Open Patent Publication No. 2006-319116, each interconnect layer insulating film is not modified from the surface to the bottom face, but only the upper portion of an interlayer insulating film is modified.
According to Japanese Laid-Open Patent Publication No. 2006-190872, ultraviolet irradiation is performed to increase the density in the surface portion of each porous interconnect layer insulating film. By the technique disclosed in Japanese Laid-Open Patent Publication No. 2006-190872, each interconnect layer insulating film is not modified from the surface to the bottom face, but only the surface portion of each interconnect layer insulating film is modified.